ABSTRACT Background: Over the last decade, a significant area of Zagros forests, especially in Ilam Province, west of Iran, has been affected by the phenomenon of oak decline. The most basic item for fighting the decline of these forests is to know site suitability, the parameters affecting it, determining the criteria affecting the decline and preparing a map of the decline potential of these forests. In this study, the efficiency of Maxent on preparing site suitability map of Dalab and Bankol and the most important criteria affecting P.Oak decline was investigated by TOPSIS. The integrated valuation of ecosystem services and tradeoffs (InVEST) was used to prepare a zoning map of decline potential of P.Oak site. Validation of maps was done with receiver operating characteristic curve (ROC) and field visits. Results: The results showed that pc-forest, distance from rivers and temperature are the most important criteria of the distribution of P.Oak. In addition, many parts of both sites were found to lack site suitability. The results of TOPSIS showed that the most important criteria of P.Oak decline are socio-economic criteria. Conclusions: Decline potential in Bankol was much higher and the pressure caused by stressful criteria was higher in this site. The results showed 6 general stresses of land use change, grazing, pests, charcoal disease, fires and tourism in two sites. Dalab has shown a better condition in terms of decline potential. The reason for this is the operation of conservation management in this site. The obtained results show the efficiency of the used methods.

ABSTRACT Background: During the past decade, the phenomenon of Oak decline has affected valuable Zagros Oak Forests in western Iran. Quercus brantii as the most important tree species of these forests has been damaged more than any other species. Many factors are involved in this phenomenon. The purpose of this study was to identify areas with high potential for decline and determine the most important factors affecting it. In this study, using multi-criteria evaluation methods based on the Geographic Information System (GIS) Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method and fuzzy logic, the map of decline potential of two selected stands (Dalab and Cheghasabz) in Ilam Province was prepared to reveal the high-risk areas of decline. The analytical hierarchical process was used to determine the weight of the factors. Results: The results showed that both selected stands had decline potential. However, the Dalab stand at 25% and the Cheghasabz, at approximately 60% of the stand has an extreme potential for decline. Rainfall factors, pests, and diseases also have the greatest effect on Oak forest decline. Conclusion: Due to socio-economic problems such as land use change, fire, tourism, grazing, and pruning, the Cheghasabz is more prone to decline than the Dalab, which was a forest reserve. The multi-criteria evaluation model used in the study can be a guide in identifying high-risk areas in other parts of the Zagros forests. The large area of critical areas in these two regions reveals the need for planning to implement support operations to reconstruct damaged ecosystems.